The field of the invention is dispensers for chemical concentrates, and particularly the dispensing of chemical concentrates, from a container, which can cause an increase in pressure in the container.
Dispensers of the type concerned with in this invention are disclosed in U.S. Pat. No. 6,708,901, which teachings are incorporated herein. The dispensing apparatus disclosed in this patent can control the flow of carrier liquid and chemical product in a precise and controlled manner. However, there are instances where the chemical product which is stored in the container from which the chemical product is dispensed can cause an increase in pressure. If the contents of the container are not vented, a problem can arise.
Vented type dispensers are disclosed in U.S. Pat. No. 1,638,550 and No. 3,157,360. Venting systems for containers are described in U.S. Pat. No. 4,993,602 and No. 6,196,409.
The prior art does not provide a venting of excess pressure from a container which is employed in conjunction with a dispenser employing an eductor. Neither does the prior art provide such a venting of excess pressure from a dispenser which includes an air vent passage that is closed when the dispenser is not in operation.